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Alternator Pulley nut.

rbibb

Well Known Member
Ok I had my Plane Power 60 amp alternator pulley nut come off in flight. The pulley remained but the belt got trashed, etc. the good folks at Hartzell send me a new nut gratis but had no info on how to otherwise repair.

The unit is based on some model Nippo Denso oem model but no joy finding any info there.

The question is: How does one torque this nut? There is no way to hold the shaft while torquing the nut. I?ve removed rear cover, etc. to see if there was some access from the rear. No joy.

Unit has performed well other than this unusual incident.

All opinions welcomed and respected until proven unworthy. :)
 
Is it possible to hold the pulley with a strap wrench while torquing the nut? Same method as when you put a drive gear on a magneto.
 
Is it possible to hold the pulley with a strap wrench while torquing the nut? Same method as when you put a drive gear on a magneto.

The pulley isn?t keyed to the shaft, it?s just clamped in place by the nut. That was what I originally thought would work. No key, no joy.

Going to try impact wrench...we shall see.
 
Yes, impact wrench

You can use the belt wrapped around the pulley to make a temporary strap wrench while you use the impact wrench. Best to use a glove on the hand holding the belt.

Cheers, David
KBTF A&P
 
I took my spare clone alternator to a shop to have a new pully installed. The guy used an air-impact driver to remove and replace the nut. No other way I could see to do same.
 
Missing NUT

During last Condition Inspection the A&P noticed the large nut missing from Alternator Pully. Pully was tight and working fine. Really NO idea how many hours ago it departed. Called Hartzel and was advised: We can sell you another nut but we prefer you send that Alternator to us to have the Nut. We need to inspect that shaft before installing another nut too. I sourced another new Alternator with two delivery and replaced the whole thing. (Guess 'Im too impatient! )
 
During last Condition Inspection the A&P noticed the large nut missing from Alternator Pully. Pully was tight and working fine. Really NO idea how many hours ago it departed. Called Hartzel and was advised: We can sell you another nut but we prefer you send that Alternator to us to have the Nut. We need to inspect that shaft before installing another nut too. I sourced another new Alternator with two delivery and replaced the whole thing. (Guess 'Im too impatient! )

Given two different folks have had the nut come off new alternators, I would say the method the manuacturer is using to torque it is flawed and would zip it on with an impact instead. No sense shipping it back to have the same flawed method done again.

I believe the shaft has a morse taper and if the pulley is still on the alternator, it is being held by it's taper fit. and no damage has occured. These are pretty binary. They are either tight and don't move or loose and come off, without a nut.

Larry
 
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Yup, the impact wrench is your friend in these situations.

Yeah... trip to Harbor Freight for $22 impact wrench and 20 minutes later problem solved.

Test flew it an hour today and all seems to be holding together ok.
 
Is there a trick to using an impact wrench to tighten an alternator pulley nut like this?

My total impact wrench experience is with automobile wheel lug-nuts, and with removing the nut on the alternator. My cheapo air powered impact wrench has a button to change the direction, and the button has 1-5 numbers indicated on it which can be selected by rotating. The button will rotate freely 360 degrees without detents. I don't see much difference no matter how I rotate that button.

The impact wrench documentation says it will do about 450 ft-lbs at 90 psi (converted from metric to freedom units). I'm guessing that the torque needed on this M14x1.5 nut is probably closer to 70 ft-lbs, so anyone know if there is a trick to using an impact wrench to tighten an alternator pulley nut?

The Google consensus seems to be to use the TLAR method - hit it with the impact wrench and call it a day.
 
Is there a trick to using an impact wrench to tighten an alternator pulley nut like this?

My total impact wrench experience is with automobile wheel lug-nuts, and with removing the nut on the alternator. My cheapo air powered impact wrench has a button to change the direction, and the button has 1-5 numbers indicated on it which can be selected by rotating. The button will rotate freely 360 degrees without detents. I don't see much difference no matter how I rotate that button.

The impact wrench documentation says it will do about 450 ft-lbs at 90 psi (converted from metric to freedom units). I'm guessing that the torque needed on this M14x1.5 nut is probably closer to 70 ft-lbs, so anyone know if there is a trick to using an impact wrench to tighten an alternator pulley nut?

The Google consensus seems to be to use the TLAR method - hit it with the impact wrench and call it a day.

I dial down the force on the impact for installing a pulley nut. However, it is not overly critical. The key is to grip the pulley tightly with your other hand. This allows slippage of the pulley before any serious amount of torque gets applied to the nut. It is a taper fit, so 70 ft lbs is not required.

The adjustments cannot produce noticable change when free wheeling, except REALLY LOW levels.
Larry
 
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This way works.

You can use the belt wrapped around the pulley to make a temporary strap wrench while you use the impact wrench. Best to use a glove on the hand holding the belt.

Cheers, David
KBTF A&P

+1 for getting it going. If not enough, mark the nut clocking and hit with impact wrench for an additional flat.

I was able to use the belt method and torque the nut on a repaired PP EI60.

Nothing but the appearance of this alternator is Denso.
 
I dial down the force on the impact for installing a pulley nut. However, it is not overly critical. The key is to grip the pulley tightly with your other hand. This allows slippage of the pulley before any serious amount of torque gets applied to the nut. It is a taper fit, so 70 ft lbs is not required.

The adjustments cannot produce noticable change when free wheeling, except REALLY LOW levels.
Larry

Larry, it is NOT a taper fit. I am absolutely positive.
 
It is definitely not a tapered shaft. That combined with CCW rotation means the V-belt drive torque imparted into the pulley is trying to unscrew the nut, which is why it needs to be torqued to every bit of the 70-ish ft-lbs as called out.
 
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